Boiler feed system



July 27, 1954 H. HILLlER 2,684,664

, BOILER FEED SYSTEM ,Dri ginal Filed March 1, 1949 s Sheets-Sheet 1PUMPZZ ,9 PUMP6 M QQ vs, 0 v. 5 QQ A Mrzwzav-waawaawaae luvs/v70)? 0.4mmHILL 'IER July 27, 1954 H, HILLIER 2,684,664

BOILER FEED SYSTEM Original Filed March 1, 1949 3 Sheets-Sheet 2 M/VEIVT 0!? HAROLD HILL IE I? July 27, 1954 H. HILLIER BOILER FEED SYSTEMOriginal Filed March 1 1949 3 Sheets-Sheet I5 PUMP 22 OR 22" PUMPS22A/VD 22" PUMPS 6" AND a" DISCHARGE PRESSURE LBS PER 30. INCH W47'ERFLOW-GALE. PER HR.

PUMP 22' OR 22" PUMPS 22' AND 22 'PUMPS 6' AND 6" D/SCHARGE PRESSURE 6LBS. PER 50, INCH WATER FLOW-GALE. PER HR.

l/V VE N TOR HAROLD HILL/ER Patented July 27, 1954 UNITED STATEd TENTOFFICE BOILER FEED SYSTEM Harold Hillier, Glasgow, Scotland, assignor toG. & J. Weir Limited, Cathcart, Glasgow. Scotland, a company of GreatBritain and Northern Ireland Claims priority, application Great BritainJanuary 28, 1949 Claims.

This invention relates to boiler feed systems with provision forremoving gaseous impurities from the feed water.

This application is a division of my pending application Serial No.78,960 filed March 1, 1949 for Boiler Feed System now Patent No.2,656,823

granted October 27, 1953'.

It is known to make use of a deaerating or steam regenerative typecondenser for the purpose of deaerating all condensate passing throughsuch condenser, the condensate being thereafter conveyed tothe boilersthrough a closed feed system wherein the pressure on the discharge sideof the condensate extraction pump is maintained substantially aboveatmospheric pressure so as to avoid any possible ingress ofcontaminating air. During standing conditions and starting up, and onboard ship during rapid manoeuvring and port conditions, circumstancesmay arise in which the deaeration of the feed water is not as good asduring steady normal operating conditions. Further, the extremely highboiler pressures which are now becoming more commonly used necessitatedeaeration of the feed water to the greatest possible extent under allconditions of operation whether standing, in port, warming up,manoeuvring, or in steady operation.

The present invention provides an improved boiler feed system in whichthe feed water discharged by the condensate extraction pump to theboiler feed pump passes preferentially through a deaerator wherein adeaerating action is superimposed upon the deaerating action to whichthe feed water has already been subjected in the condenser. Thisdeaerator may also be used for port service on board ship when the maincondensing plant is closed down, either operating in series with anauxiliary condensing plant or in parallel, as may be preferred.

In accordance with the invention, the discharge of the main condenserextraction pump is connected direct to the boiler feed pump suction andin parallel also to the float-controlled inlet of a deaerator, with theobject of passing the discharge of such pump preferentially into thedeaerator in which it is subjected to deaerating action and from whichit is subsequently removed by a deaerator extraction pump whichdischarges into the closed feed line nearer to the boiler feed pumpsuction than the point in the closed feed line connected to the inlet tosaid deaerator. With this arrangement the boiler feed pump pref erablytakes water from the discharge of the deaerator extraction pump, but canalso take water, when necessary, direct from the discharge of thecondenser extraction pump. The boiler feed system claimed hereinincludes a non-return valve in the closed feed line between thecondenser extraction pump discharge to the deaerator and the deaeratorextraction pump discharge to the boiler feed pump, whereby to preventthe deaerator extraction pump from discharging back into the deaerator.The relation of the discharge pressure capacity characteristic of thedeaerator extraction pump and the discharge pressure capacitycharacteristic of the condenser extraction pump is such that up to thepro-determined maximum capacity of the deaerator extraction pump theboiler feed pump takes its supply of water preferentially from thedeaerator extraction pump discharge. The quantity of water passingthrough the deaerator at any given boiler load is determined by thedischarge pressure capacity characteristics of the condenser extractionpump and the deaerator extraction pump under the control of afloatoperated water inlet valve on the deaerator, the float beingoperated by the rise and fall of the water level in the bottom of thedeaerator whereby a fall in the float increases the flow of water intothe deaerator and vice versa.

Heat exchange apparatus may be provided in the discharge line from thecondenser extraction pump for heating the feed water before it can passinto the deaerator, and deaeration may be effected in the deaerator bythe flash of such heated feed water, the boiling pressure in thedeaerator being maintained by a connection to the main condenser wherebyvapor and noncondensable gases can flow to the main condenser, or bymeans of a steam ejector which discharges into a condenser from whichthe air can escape to the atmosphere. An air ejector may be arranged todischarge to the main condenser whereby boiling pressure can be ensuredin the deaerator without any heating of the condensate before it passesinto the deaerator.

Additional heating steam may be supplied to the deaerator so thatdeaeration is assisted by heating of the water in its passage throughthe deaerator, air and non-condensable gases being withdrawn asmentioned above.

The capacity of the deaerating vessel may be equal to the capacity ofthe boiler feed pump or the capacity of the deaerator may be less orgreater than the boiler feed pump capacity by a predetermined amount.For port use, on board ship, a feed supply pump may be arranged to drawwater from a feed tank and discharge through the float operated valve tothe deaerator, the arrangement being such that all feed water to bedeaerated must pass by way of the feed tank to the deaerator or fromdrainage lines direct into the deaerator wherein it is subjected todeaerating action before it is delivered by the deaerator extractionpump to the suction of the boiler feed pump. Feed pumps of differentcapacity may be available for port use and for sea service,respectively, or there may be provided restriction means whereby underport operating conditions the sea service feed pump is restricted to acapacity not exceeding the capacity of the deaerator. Again, a directconnection may be made from the boiler feed pump suction to the 1 mainfeed tank through a non-return valve which will normally be kept closedby the pressure of the deaerator and condenser extraction pumps, butwill permit the feed pump to draw water direct from the feed tank incase of emergency.

With the arrangements proposed all feed water in normal operation willbe subjected to the deaerating effect of the main condenser and.subsequently to the deaerating effect of the deaerator whereby themaximum possible deaeration is obtained before the feed water isdelivered by the boiler feed pump to the boilers. In the event ofderangement of the deaerator the boiler feed pump will take water directfrom the condenser extraction pump, such water having been subjected tothe deaerating action of the main condenser. In the event of derangementof both the condensing plant and the deaerating plant, the feed pump candraw water direct from the feed tank.

The accompanying drawings illustrate convenient arrangements ofapparatus according to the invention.

Fig. l is a diagrammatic arrangement of a closed boiler feed systemprovided with additional means for deaerating the feed water inaccordance with the invention;

Fig. 2 illustrates the preferred arrangement of discharge pressurecapacity characteristics for the condenser extraction pump and thedeaerator extraction pump;

Fig. 3 shows diagrammatically two or more boiler feed systems inaccordance with the invention connected so that they may be operatedsatisfactorily in parallel;

Fig. 4a. and Fig. 4b illustrate the preferred arrangements of dischargepressure capacity characteristics for the condenser extraction pump anddeaerator extraction pump when operating two or more closed feed systemsin parallel in accordance with the invention.

reaching the well 3 in the base of the condenser. Air and othernon-condensable gases are drawn off through air off-takes 5 arrangedsubstantially remote from the water level in the base of the condenserso that a negligible air pressure exists on the surface of the water inthe well 3. All condensate passing through the condenser is thussubjected to the deaerating action of the steam in the base of thecondenser before it is withdrawn by the condensate extraction pump 6.The condensate extraction pump discharges through heat exchangeapparatus such as the air ejector l and the feed heater 8 to the point 9where it is provided with alternative paths direct to the boiler feedpump H3 or to the deaerating apparatus Ii. The well 3 in the condenser 2is provided with a float I2 coupled as illustrated diagrammatically tomake-up and overflow valves l3 and H3, respectively. When the demand ofthe feed pump [ii is less than the condensate formation in the condenser2 and the water level in the deaerator H is high a rise in water levelin the condenser 2 takes place operating the float l2 which opens theoverflow valve l4 and allows surplus water to pass from the condensatedischarge line leading from pump 6, after the outlet from the heater 8,by way of pipe E5, the overflow valve H3 and the pipe IE to an externalfeed tank If. When the demand of the feed pump Ill is in excess of thecondensate formed in the condenser 2 the water level in the base of thecondenser will fall and the float [2 will open the make-up valve i3,permitting water to pass from the feed tank I! by way of the pipe 16,the make-up valve 13 and the pipe It into the condenser 2 where thewater will be sprayed and deaerated. The make-up Water passing into thecondenser 2 will fall to the base of the condenser from which theextraction pump 6 will discharge it into the closed feed system.

The main feed pump l0 discharges the water supplied to it by way of theheat exchanger [9, and the boiler feed regulator 25] into the boiler 2I. Heating steam, which may be bled steam from the main turbine l, orexhaust steam, or heating steam from any source, may be supplied to theheat exchangers 8 and [9.

The deaerator H is provided with a deaerator extraction pump 22 whichdischarges by way of a pipe 23 to the closed feed system where it entersthe closed feed system at the point 24. The point Rd is on thedown-stream side of the closed feed system relatively to the point 9, sothat Water discharged by the deaerator extraction pump 22 preferentiallyflows into the suction of the feed pump it and any water which is nottaken by the boiler feed pump I0 passes by way of the pipe 25 and pipe26 to the deaerator inlet valve 27. The valve 2? is controlled by thefloat 28 which follows the water level in the base of the deaerator H.Water passing through the float-controlled valve 2"! passes by way of aheat exchanger 25? into the top of the deaerator i l where it passesthrough spraying nozzles 38, or perforated plates, into the body of thedeaerator which may be provided with spraying trays 3| through which thewater cascades to the base of the deaerator. The feed water, in passingthrough the heat exchangers i and 8, is heated before it is sprayed intothe deaerator ii. A certain proportion of vapor, together with anynon-condensable gases, is withdrawn from the top of the deaerator l iand passed by way of a pipe 32 to the main condenser 2. Alternatively,the non-condensable gases may be withdrawn by a steam-operated ejector33 'valve 42 to the auxiliary condenser 43.

which discharges into the de-vaporizer:29,-the-resultant condensatebeing drained through a trap 34 into the deaerator l i, in which lattercase, the air and non-condensable gases are discharged to theatmosphere. If desired, heating steam from any suitable source may bepassed into the deaerator through a pipe 35 provided with a controlvalve 36 to maintain a desired predetermined pressure in the deaerator lI.

If the feed pump H! is-driven by a turbine 31,

the exhaust steam from such turbine may be led into the deaerator or asuitable heat exchanger asshown, surplus exhaust steam from the turbinepassing by way of a surplus steam valve 38 to the main condenser.

With a suitable selection of the capacity and the discharge pressure ofthe deaerator extraction'pump 22, all water passing to the boiler feedpump I0 is preferentially taken from the discharge of the deaeratorextraction pump 22. When the water in the condenser is at a levelbetween its upper and lower limits, the valve I4 is closed, and thewater discharged by the condensate extraction pump is constrained topass by way of the pipe 26 and float-controlled valve 21 into thedeaerator H from which it is withdrawn by the deaerator extraction pump22 and discharged to the suction of the boiler feed pump It). If thecapacity of the deaerator extraction pump at any time is greater thanthe quantity of water required by the boiler feed pump, thebalance willpass backwards by way of the pipe 25, the

pipe 26, and the float-controlled valve 27 into will discharge the Waterby way of the pipe 23 to the suction of the auxiliary feed pump 39 whichwill then discharge the deaerated water through the heat exchanger i9 tothe boiler. The auxiliary feed pump 39 may be driven by a steam turbine4! which exhausts into the heating steam supply line 35 to the deaeratorl I, any surplus steam passing by way of a surplus steam The auxiliarycondenser 43 may be provided with a condensate extraction pump 44 whichdischarges any condensate from the auxiliary condenser through a heatexchanger 45 and a pipe 46 to the feed tank ll, preferably into thesuction of the deaerator supply pump 40.

It will be seen that, in the main condensing system, all water passingthrough the condenser '2 is subjected to the deaerator action of thecondenser 2. Such water is subsequently discharged into the closed feedsystem by the condenser extraction pump 6 and the arrangement is suchthat the water discharged by the pump B is preferentially divertedthrough the deaerator l I from which it is removed by the deaeratorextraction pump 22 whence it is discharged into the suction of theboiler feed pump to, the arrangement being such that all water passingto the boiler feed pump issubjected to the deaerating effect of vensured. In the event of derangement of the deaerating plant II thecondensate extraction pump 6 can discharge water direct to the suctionofthe boiler feed pump Ill through the pipe 25. In the event of the closedfeed system being deranged, the boiler feed pump Hi can draw waterdirect from the feed tank I! by way of the pipe 23, the non-return valve49 and the pipe 50 connecting to the feed tank 11. The non-return valve49 is maintained in its closed position in normal operation by thedischarge pressure set up by the deaerator extraction pump 22 and thecondensate extraction pump 6. Other non-return or check valves areprovided in the system and indicated in the same manner as the valve 49,sometimes adjacent to a cut-off valve.

Referring to Fig. 2, it is preferred that thecapacity of the deaeratingapparatus should be equal to the maximum feed flow through the feedpump, but for economy reasons it may be acceptable to provide adeaerating apparatus of smaller capacity. Fig. 2 shows the preferredrelative discharge pressure capacity characteristics of the condenserextraction pump and the deaerator extraction pump. Assuming that thecondenser extraction pump 6 is designed for a discharge pressurecapacity characteristic shown by the line AB, the point E represents themaximum feed flow required by the boiler feed pump. There will be adifference in pressure between the vacuum in the condenser and thevacuum in the deaerator, and after allowance is made for this, thedeaerator extraction pump 22 is designed for a discharge pressurecapacity characteristic such as CD, where CD intersects thecharacteristic AB at the point E corresponding to maximum feed flow.This ensures that the pressure at the discharge of the deaeratorextraction. pump will be equal to or greater than the discharge pressureof the condenser extraction pump atall flows between zero and maximumfeed flow. Provision may be made for variable speed of the driver of thedeaerator extraction pump so that the discharge pressure capacitycharacteristic CD can be raised or lowered as desired. The dischargecharacteristics AB and CD are measured at the common point 9 in thedischarge lines after allowance for friction between the respectivepumps and the common point 9 in the discharge lines. The pressures atthe boiler feed pump suction will be determined by the balancing of thequantity of water discharged by the condenser extraction pump and thequantity of water discharged by the deaerator extraction pump asdetermined by their characteristics fora common discharge pressure andthe fiow required through the boiler feed D p- Assuming, for example,that the boiler feed regulator 20' closes and reduces the feed flow tothe boilers, so that the main extraction pump discharge pressure at thepoint 9 moves to GHJ, then the quantity of water passing to the boilerswill be equal to OK which is the quantity of water discharged by thecondenser extraction pump, which passes through the deaerator, and thequantity of water discharged by the deaerator extraction pump is equalto CL where the quantity OK passes into the boiler feed pump while thequantity KL passes back through the floatcontrolled inlet valve 2'! onthe deaerator into the deaerator again. The quantity of water discharged by the condenser extraction pump 6 is the quantity of waterwhich passes through the boiler feed pump l0, so that, if the feedregulator closes further until noflow is passing into the boiler, thepressure will rise to the line AM at the suction of the boiler feedpump, no water will be discharged by the condenser extraction pump intothe deaerator, and the deaerator extraction pump will discharge aquantity equal to ON which quantity will flow back through thefloat-controlled valve into the deaerator and will be in continuouscirculation through the deaerating apparatus. It will be seen that theflow through the deaerator varies between the maximum feed flow OF and aminimum flow ON while the flow from the condenser extraction pump variesfrom the maximum OF to zero. Since the capacity and discharge pressureof the deaerator extraction pump 22 are always equal to or greater thanthe condenser extraction pump 6, the water taken by the boiler feed pumpwill preferentially be the water discharged by the deaerator extractionpump and will therefore have been twice subjected to the deaeratingaction of, first, the main deaerating condenser and, second, thedeaerating apparatus II. The arrangement is such therefore as to ensurethe maximum possible deaeration of all feed water discharged by theboiler feed pump to the boilers.

The characteristic CD may be arranged to be more closely similar to thecharacteristic AE, or the point of intersection between the two characteristics may be arranged to be less or greater than the maximum feedflow OF to the boilers.

Referring to Fig. 3, the same numerals are used to designate similarparts except that a prime sufiix is attached to those of the uppersystem and a double prime suflix is attached to those of the lowersystem in Fig. 3.

When two or more closed feed systems such as have been described arerequired to operate in parallel, there are inevitable inequalities inthe quantities of steam evaporated by the several boilers 2| and 2 I andin the quantities of feed water delivered by the respective feed pumpsHi and To look after such inequalities, cross connecting pipes andvalves are arranged as shown diagrammatically in Fig. 3. A crossconnection is provided between the external feed tanks ll and Il" sothat any differences in the weight of water discharged through theexternal feed tanks H and I1 and through the overflow valves i4 and M"or other sources of supply can balance out through the cross connection5|.

To permit two or more closed feed systems to be operated in parallelwith only one deaerator H or H" in operation, a cross connection 52 isprovided between the discharges of the condenser extraction pumps 6' and6" so that the pumps have a common discharge line to the deaerator H orii" which is in operation. Isolating valves are provided so that, if onedeaerator is shut down, all connections to that deaerator are closed,and the condensate is discharged by the condenser pump associated withthat deaerator through the cross connection pipe 52 to the otherdeaerator which is in operation with the other condenser extractionpump.

In the same way a cross connection line 53 may be provided between thedischarge lines of the deaerator extraction pumps 22 and 22" so that thedeaerator extraction pump on the deaerator i i or I I" which is inoperation can discharge through such connection 53 to any of the severalboiler feed pumps l9 and it! which may be in service. The said crossconnection 53 will enable the several deaerator extraction pumps 22 and22 to deliver in common to a single boiler feed pump or more feed pumpswhich may be in service. Inequalities in the fiow through the severalcondenser extraction pumps 6 and 6 will cause the water levels in thecondenser wells to rise or fall, thereby causing the make-up valves l3and. [3 or overflow valves 14 or I l to open and pass water into or outof the several systems, the differences between the systems beinglevelled out through the cross connection 5| between the external feedtanks H and N. If there are more than two systems, cross connections areprovided between all the several pumps and the several feed pumps. Onecommon feed tank may be arranged to serve several closed feed systems,and, where several feed tanks are used, the effect of using the crossconnection 5| is to operate the several feed tanks as one common feedtank. The cross connections 52 and 53 enable any single deaerator H orH" to be in operation or two or more deaerators to be in operation inparallel with a common discharge to any feed pump or feed pumps whichare in operation.

The action of the float-controlled valves is such that the whole systemis completely automatic from no load to full load and vice versa, andthe operation of the float controls ensures that the pumps in the systemhave a satisfactory suction head at all times and are constrained tooperate at all times along their natural discharge pressurecharacteristics, while the changes in flow through the deaerator arereduced to a minimum so that the pressure and temperature conditions inthe deaerator are the optimum for eficient deaeration and thesatisfactory operation of the pumping units.

The deaerator may be operated without any additional heating and toensure adequate deaeration there may be provided an ejector 58 toWithdraw the air and non-condensable gases from the deaerator anddischarge to a suitable place under vacuum such as the main condenser 2.

Referring to Figs. 4a and 41), it is preferred that th capacity of thedeaerating apparatus should be equal to the maximum feed flow throughthe pump but for economy reasons it may be acceptable to provide adeaerating apparatus of smaller capacity. Figs. 4a. and 4b showpreferred relative discharge pressure ca pacity characteristics of thecondenser extraction pumps and the deaerator extraction pumps suitablefor the parallel operation of two or more closed feed systems inaccordance with Fig.3.

Referring to Fig. 4a, the condenser extraction pump discharge pressurecapacity characteristic is shown by the line AB, where point Erepresents the maximum feed flow required by the boiler feed pump of onesystem. If two condenser extraction pumps are in service in paralleloperation, the combined discharge pressure capacity characteristic of thtwo pumps is as shown by the line AB2, where point E2 represents thecombined maximum feed flow required by the boiler feed pumps of the twosystems. If one boiler feed pump only is in service, the pressuredeveloped by the combined condenser extraction pumps at the maximum feedflow for that boiler feed pump is as shown by the point P.

l'he deaerator extraction pump is preferably designed for a pressurecapacity characteristic such as CD, where CD intersects the maximum feedflow line at the point Q, where this point is equal to or greater thanthe point P. This ensures that the pressure at the discharge of 9 thedeaerator extraction pump will be equal to or greater than the dischargepressure of the condenser extraction pump at all flows between zero andmaximum feed flow with one boiler feed pump in operation.

If there arein operation two boiler feed pumps and two deaeratorextraction pumps, the combined characteristic of the two deaeratorextraction. pumps will be as shown by the line CD2 where Q2 is thedischarge pressure of the two pumps at the maximum feed flowcorresponding to two boiler feed pumps in operation.

It will be seen that there is a considerable difference in. pressurebetween the discharge pressure capacity characteristic CD of a deaeratorextraction pumpv and the characteristic AB of the condenser extractionpump, and, to avoid overloading the deaerator extraction pump in backflowto the cleaerator,.non-return valves 59 and 60 are preferablyprovided in the system according to Fig. 3 to prevent such anoccurrence, the non-return valves 59 and 69 being maintained in theirclosed position in normal, operation by the discharge pressure set up bythe respective deaerator extraction pumps 22' and 22 which is in excessof the discharge pressure of the respective condenser extraction pumps6' and 6". In the event of a failure of either or both deaeratingplants, the non-return valve or valves will open and permit thecondenser extraction pump or pumps to discharge direct to the suction ofthe boiler feed pump or pumps.

Referring to Fig. 4a, it will be seen that there will be a difference inpressure between the characteristics of the deaerator extraction pumpsand the condenser extraction pumps under any conditions of working whichwill maintain the said non-return valve in the closed position duringnormal operation.

Referring to Fig. 4b, the conditions illustrated in Fig. 4a may in somesystems result in excessively high discharge pressures from thedeaerator extraction pump. The condenser extraction pump driver maytherefore be provided with means whereby the speed of that pump can bevaried.

The line AB shows the discharge pressure capacity characteristic for thecondenser extraction pump when operating under the solo system, the lineA132 representing the combined characteristic of two condenser pumpsoperating in parallel. Means is preferably provided for varying thespeed of the condenser pump, so that the combined characteristic'islowered to (1172 where ab is the characteristic for each pump operatingalone. This will enable the deaerator extraction pump to be operated ata discharge pressure capacity characteristic corresponding to CD with acombined characteristic for two pumps corresponding to CD2, the saidcharacteristic being substantially lower than the correspondingcharacteristics in Fig. la.

For solo operation the condenser extraction pump may be operated alongthe line AB with the deaerator extraction pump cperating along the lineCD. For parallel operation between the two systems, the condenser pumpcharacteristic is lowered to cab with a combined characteristic of M72in connection with which either a single deaerator extraction pump witha characteristic of AB or two deaerator extraction pumps with acharacteristic of A132 can be operated satisfactorily.

Since the capacity and discharge pressure of the deaerator extractionpump or pumps are 10 always equal to or greater than the condenserextraction pump or pumps, the water taken by the boiler feed pump willpreferentially be the water discharged by the deaerator extraction pumpand will therefore have been twice subjected to the ate satisfactorily,and the pumps are constrained to operate at all times along theirnatural discharge pressure capacity characteristics. Under normaloperating conditions, the whole of the water discharged to the boilersis first subjected to the deaerating action of the condenser 2 andsubsequently to the deaerating action of the deaerator H, and anysurplus of water discharged by the respective pumps is subjected to arepeated deaerating action before passing to the boiler feed pump fordischarge to the boilers.

It is to be understood that the apparatus shown may be modified indetail and that the constructions illustrated and described herein aretypical convenient forms.

I claim:

1. A closed feed system for a steam boiler including a condenser for thecondensation of steam initially generated in the boiler, a condensateextraction pump connected into the lower portion of the condenser, aboiler feed pump connected into the boiler, a feed line connecting thedischarge of the condensate extraction pump with the suction side of theboiler feed pump, a deaerator for deaerating the water normally suppliedto the boiler by the boiler feed pump, a deaerator extraction pumpconnected into the lower portion of the deaerator and having itsdischarge connected into said feed line, a water supply conduit one endof which is connected to said feed line upstream of the dischargeconnection from said deaerator extraction pump and the other end ofwhich is connected to said deaerator, a float-controlled water inletvalve in said Water supply conduit connected into the deaeratorresponsive to changes in the water level in the deaerator, said valveopening on a fall of the water level in the deaerator and closing on arise of the water level in the deaerator, and a non-return valve in aportion of the feed line between the entry end of the water supplyconduit and the discharge connection from the deaerator extraction pump,said non-return valve being arranged in the feed line to permit flowtherethrough toward the boiler feed pump and prevent flow in theopposite direction.

2. A closed feed system for a steam boiler including a condenser for thecondensation of steam initially generated in the boiler, a condensateextraction pump having its suction side connected into the lower portionof the condenser for withdrawing condensate therefrom, a boiler feedpump having its discharge side connected into the boiler for deliveringfeed water thereto, a feed line connecting the discharge side of thecondensate extraction pump with the suction side of the boiler feedpump, a deaerator for deaerating the water normally supplied to theboiler by the boiler feed pump, a conduit for supplying water to thedeaerator from said feed line one end of which is connected into saidfeed line downstream of the condensate extraction pump, the other end ofsaid conduit being connected into said deaerator, means associated withthe deaerator for collecting the deaerated water produced in thedeaerator, a deaerator extraction pump having its suction side connectedinto the lower portion of said means associated with the deaerator forwithdrawing deaerated water therefrom and having its discharge sideconnected into said feed line between the point of connection of thefeed line with the suction side of the boiler feed pump and the pointwhere said conduit is connected into the feed line, said deaeratorextraction pump delivering deaerated water into the feed line and to theboiler feed pump, a nonreturn valve in the feed line between saidpoints, said non-return valve being provided in the feed line andarranged therein to prevent flow of water from the deaerator extractionpump into the deaerator in the normal operation thereby to avoidoverloading the deaerator extraction pump, said non-return valve beingmaintained in closed position in normal operation by the dischargepressure of the deaerator extraction pump and being opened in the eventof failure of the deaerator thereby permitting the condenser extractionpump to discharge directly through the feed line to the suction side ofthe boiler feed pump, a control valve in said water supply conduit forcontinuously controlling the flow of water from said feed line into thedeaerator, a float responsive to changes in the level of a body ofdeaerated water, said means associated with the deaerator, said floatbeing operatively associated with said control valve for respectivelyopening and closing said control valve on the fall and rise respectivelyof the water level in the body of deaerated water under all conditionsof operation, whereby a body of deaerated water is maintained in normaloperation for delivery by the deaerator extraction pump to the feed lineand the boiler feed pump.

3. A closed feed system as claimed in claim 2, including an externalfeed water tank, means for conducting the water discharged by thecondensate extraction pump in excess of that admitted to the deaeratorby the control valve into the external feed tank, and means for passingwater directly from the external feed water tank into said water supplyconduit upstream of the control valve in said conduit for deliverythrough the control valve to the deaerator.

i. The method of operating a closed feed water system including a steamboiler, a boiler feed pump, a condenser for the condensation of steaminitially generated by the boiler, a condensate extraction pump havingits suction side connected into the lower portion of the condenser, afeed line connecting the discharge side of the condensate extractionpump with the suction side of the boiler feed pump, and a deaerator fordeaerating the water to be supplied to the boiler, which methodcomprises passing a stream of condensate from the condenser into thefeed line and from said line under pressure into the upper portion ofthe deaerator ior deaeration therein, deaerating the stream ofcondensate introduced into the upper portion of the deaerator,collecting and maintaining a body of the deaerated water produced in thedeaerator, passing a stream of deaerated water from said body of waterunder pressure into the feed line and through the boiler feed pump fordelivery to the boiler as feed water therefor, maintaining a higherpressure on the stream of deaerated water than that on the stream ofcondensate in said feed line under normal operating conditions andpreventing the flow of deaerated water in the feed line toward thecondensate extraction pump, passing condensate directly through the feedline from the condensate extraction pump to the boiler feed pump in theevent the pressure on the stream of deaerated water falls below that onthe stream of condensate delivered by the condensate extraction pump,withdrawing air and non-condensable gases from the upper part of thedeaerator by applying suction thereto, and decreasing and increasingrespectively the flow in said stream of condensate introduced into theupper portion of the deaerator in response to the rise and fallrespectively of the level of the body of deaerated water, whereby saidbody of deaerated water is maintained under normal operating conditionsas the source of supply of deaerated feed water for the boiler.

5. A closed feed system for a steam boiler including a condenser for thecondensation of steam initially generated in the boiler, an externalfeed tank, a condensate extraction pump having its suction sideconnected into the lower portion of the condenser for withdrawingcondensate therefrom, a float-controlled inlet valve for said condenser,said valve being closed at an intermediate water level in the condenserbase and full open at a lower level to permit make-up water to pass fromthe external feed tank into the condenser, a floatcontrolled overflowvalve for said condenser, said overflow valve being closed at anintermediate water level in the condenser well and full open at a higherlevel to permit the condenser extraction pump to discharge surplus waterto the external feed tank, a boiler feed pump having its discharge sideconnected into the boiler for delivering feed water thereto, a feed lineconnecting the discharge side of the condensate extraction pump with thesuction side of the boiler feed pump, a deaerator for deaerating thewater normally supplied to the boiler by the boiler feed pump, a conduitfor supplying water to the deaerator from said feed line one end ofwhich is connected into said feed line down-stream of the condensateextraction pump, the other end of said conduit being connected into saiddeaerator, means associated with the deaerator, for collecting thedeaerated water produced in the deaerator, a deaerator extraction pumphaving its suction side connected into the lower portion of said meansassociated with the deaerator for withdrawing deaerated water therefromand having its discharge side connected into said feed line between thepoint of connection of the feed line with the suction side of the boilerfeed pump and the point where said conduit is connected into the feedline, said deaerator extraction pump delivering deaerated water into thefeed line and to the boiler feed pump, a non-return valve in the feedline between said points, said non-return valve being provided in thefeed line and arranged therein to prevent flow of water from thedeaerator extraction pump into the deaerator in the normal operation,said non-return valve being maintained in closed position in normaloperation by the discharge pressure of the deaerator extraction pump andbeing opened in the event of failure of the deaerator thereby permittingthe condenser extraction pump to discharge directly through the feedline to the suction side of the boiler feed pump, a control valve insaid water supply conduit for continuously controlling the how or" water13 14 from said feed line into the deaerator, a float by the deaeratorextraction pump to the feed responsive to changes in the level of a bodyof line and the boiler feed pump. deaerated water, said float beingoperatively associated with said control valve for respectively e cesfiited in the fi Of this patent opening and closing said control valveon the 5 UNITED STATES PATENTS fall and rise respectively of the waterlevel in the body of deaerated water under all conditions g g fia gfi ofoperation, whereby a body of deaerated water 2626005 Sebald Jan. 20,1953 is maintained in normal operation for delivery

